Open Source Ecology - User contributions [en]

Leo.dearden

2009-11-26T08:02:38Z

Fenn: /* Beyond RepLab */

== Leo Dearden ==

I'm committed to the RepLab project.

=== Tools of interest ===

RepRap.
* support material
* for electronics
** Pick n place
** conductive material deposition
* for mold making
* for ceramics

CNC Machine Tools. Lathe, Router, Mill.
* air bearings based on graphite blocks for linear slides and spindles
* casting whole machines from epoxy/granite/carbon fiber composites
* using laser interferometers during fabrication and operation to tool up to extreme accuracy from inaccurate components and with inaccurate tools.
* fabricating low cost high performance linear motors for extremely high motion performance low to moderate load tools
* carbon fibre composite air bearing screws for high load high performance tools

Software tools
* Electronics place and route for RepRap
* Unsupervised CAM (subtractive cutting path generation)

Curing oven for composites
Vacuum mixing and casting systems for composites
Vacuum pumps
Air Compressors

=== Personal Participation ===

I will work on (in order, subject to revision)
* CNC router bootstap:
** improved spindle mounting
** 4th axis.
** Later, vacuum clamping and precision kinematic clamping.
* RepStrap (based on CNC router cartesian bot)
** single plastic extruder head
** second hot extruder head
** paste head
** low melt alloy and copper composites for extrusion
** printing circuits
** pick and place.
* Powerful and high precision machine tools as detailed above.

I'll offer advice and comment wherever it's welcome.

=== Resources ===

I have a fairly extensive personal workshop (http://fabricationsofthemind.blogspot.com/2008/10/in-praise-of-good-workshop.html).

I'm peripherally involved with the RepRap project, and will get more deeply involved as I work on my RepStrap. I'm a well liked friend of the explosively growing Noisebridge San Francisco hackerspace. I currently work for Google. I may be able to harness or evoke contributions from any of these, and I will listen for opportunities to do so.

=== Funding Model ===

I've funded my work so far from my income. In the next three years I intend to bootstrap through having more free time to taking paid work based on RepLab technology to develop and deploy machines. The things I learn in that work will be contributed open source and the money from it will support me and my work. If possible, I will replicate this model, supporting others in doing the same.

=== Time Budget ===

I'm working very full time at the moment. I can currently contribute a very little. I'll have a little more time in the spring 2010, and hope to secure one day a week to work on open source circuit printing, as part of my paid job, later 2010. Beyond that, more and more time as I can arrange it.

=== RepLab Tool List Opinions ===

Build/Defer is ever only a personal opinion. FWIW, I'm open to persuasion, and more importantly, whoever wants to Build anything, can of course get on with it. :-)

1. Laser cutter - large DIY community exists for C02 lasers

Very handy. It's basically a new tool head for a plasma table or similar. Defer.

2. ShopBot - RepTab is the Factor e Farm version

RepTab looks like a good plasma table. I'm not sure how well it will handle cutting loads. Perhaps it will require modification to do that, but some sort of gantry router will work well and should definitely be in the toolkit. Build soon.

3. Precise router for milling circuits

Precise router, for many things. If we can make it stiff and coolant proof enough, it becomes a Mill, too. If it's heat and RF resistant enough it's a plasma table. If it's fast enough it's a laser cutter, or a RepStrap. Build soon.

2 and 3 can have a lot in common. 3 is just smaller and more precise. Common designs could be mostly parametrised to provide both.

4. Plasma cutter - power circuit is main point to opensource

Yes. The head is also non-trivial, IMHO. I suggest: Defer.

5. Welder - power circuit is main point to opensource

Yes. Likewise, Defer.

6. Oscilloscope - can a computer oscilloscope cover most needs?

Yes it can. It can be just as good as (or better than) a standalone one. There are projects out there to make these already. Obtain, commercial or open source.

7. Rep(st)Rap

Build or Obtain a kit then Build our version as discussed in other posts.

8. Mill

Build

9. Drill

Hand drill, drillstand: Obtain. Pillar drill can be built as part of the Mill.

10. Lathe

Build.

11. Induction furnace - power electronics are main point to opensource

Defer.

12. Ciruit fab - automated process including pick-and-place

Build.

13. Aluminum extrusion

14. Metal casting - of ingot from induction furnace, and other molds
15. Hot rolling
16. Cold rolling
17. Forging
18. Metal shear and hole punch for up to 1" steel
19. Wire drawing

Defer all.

The heavy industrial infrastructure will be easier once we have the machine tools working. We'll also have a better idea of what we want and need.

=== Beyond RepLab ===

Air compressor

Vacuum Pump
* 0.1 mbar, >10cfm for degassing and lamination.
* 0.1 bar, >100cfm for vac clamping.
** i hear a shop vac + light duty pump and check valve works great

1 phase -> 3 phase converter.

Shaker, for casting

[[Category:RepLab Developers]]

Lathe Build

2009-11-24T19:03:13Z

Fenn: comments

=Concept=
[[Image:latheconcept.jpg]]

=Introduction=
Read this beautiful introduction on the practical aspects of a lathe in this introduction by a master of documentation, Chris Palmer - [http://hydraraptor.blogspot.com/2008/11/lathe-accesories.html]

[[Image:latheintro.gif]]
=Auger=

Ben,

So here's my plan right now. Use a hydrauilic fixture with 20 hp that can be fixed to a table readily. This is what I have already on [[LifeTrac]] - a stiff auger mechanism:

[[Image:multiauger.jpg|thumb]]

=Bill of Materials=

Here is the bill of materials:

[[File:augerbom.jpg|thumb|left|Bill of Materials]]

=Lathe=

Is it possible to convert the auger to a lathe? Sure. Take a chuck from [http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=310096648710&rvr_id=&crlp=1_263602_263622&UA=L*F%3F&GUID=1357ab741250a0265337bec7ff94d6a7&itemid=310096648710&ff4=263602_263622 here].

[[Image:chuckselfcent.png|thumb|left]]

Add a [http://www.use-enco.com/CGI/INSRIT?PMAKA=201-2826&PMPXNO=951820&PARTPG=INLMK3cross slide from Enco]. See [http://www.cartertools.com/newjose3.html review]

[[Image:crossslide.jpg|thumb|left]]

== Spec ==

What are the needs?

*Basic applications are couplers, hydraulic valve stems, and steam engine cylinders and pistons. Basic shortbed work on small workpieces. To be scaled up to a 2000 lb xy slide down the road for more efficient turning, with modifications as we go along.

*Length, diameter of object? 1 foot long up to 12 inch pipe
*Tolerances, including surface finish? 25 micron
*Manual or CNC? Manual at first, retrofit later.
*Material to be turned? Mild steel and aluminum.
*RPM range? 0-700 RPM

== Danger ==

20HP at low rpm involves HUGE forces. This is going to be seriously dangerous because many of the possible failures would be catastrophic and faster than a human operator can react. Much smaller lathes cause fatal accidents from time to time. Breakage of the tool support or failure of the workholding would quite likely lead to big bits of metal flying about. Extreme caution is justified.

The proposed XY table is not intended to support anywhere near the max load that the hydraulics can apply. Most cast iron will fail fast (shatter).

A much smaller version may be a rewarding use of time to prove the design at reduced scale, cost, risk of failure, and danger of fatal or crippling injury.

===Comments===

*The entire system is non-optimized. It is a generalized system that optimized interchangeability of parts and multipurpose performance, not specific performance. The critical distinction is sufficiency vs. optimization. Performance can be optimized by further interchangeability. This is not a finished product, but an item that works for intended applications of milling motor couplers and boring steam engine cylinders.
*20HP is max. It can be run from 1-20 hp.A 20 HP accident is no more fatal than a 1 HP and accident when it comes to machine vs. delicate human.
*XY table is absolutely too weak, but it is sufficient and cheap. Other suggestions are welcome.
*Marcin has significant experience regarding failure modes and behavior characteristics of hyraulics. Not an issue.

== Materials, Rigidity ==

Pro lathes are usually made of the fewest thickest possible pieces of cast iron, for rigidity and damping. If mild steel box and sheet, bolted or welded, was good enough then there would probably be examples out there (If it's easy and cheaper and the Chinese won't do it then it probably doesn't work). There are substantial risks that the lathe will work poorly or not at all unless it is small and made of very thick stock. If any machine tool is insufficiently rigid then the cutting edge chatters on the work piece, giving a bad finish, rapid heating of the tool, and rapid tool failure. Also, cutting forces cause the machine to elastically distort, quickly introducing very large errors.

Without defining the spec, it is difficult to design. Materials for machine tool frames include
*Aluminium alloy, on small cheap low precision or soft material tools
*Cast Iron, on most machines. Well proven.
*Synthetic or real Granite, on super precision moderate mechanical load machinery

Synthetic granite is made from ~80% granite powder with an epoxy binder, and has ~9x better damping than cast iron but much lower tensile strength. (I'd like to experiment with machine tools made from a synthetic granite modified with chopped strand carbon fibre, but that's an unproven material. [[User:Leo.dearden|Leo.dearden]])

===Synthetic Granite===

*What are costs of raw materials?
*Where do we get them?

==Cross Slide==
*What are options for an off-shelf cross slide?
*What are accuracy limits of simple cross slides made from cold rolled steel, 3/4 inch fine nuts and bolts, where nuts are pretensioned to minimize backlash? Is this a simple, robust solution that can reduce backlash to 25 microns?
*Are there any good DIY solutions for precision cross slides?

=Collaborators=
*[http://openfarmtech.org/weblog/?p=1254 Marcin Jakubowski]
*[http://www.makerbeam.com/ Sam Putnam]
*[http://fabricationsofthemind.blogspot.com/ Leo Dearden]
*http://openlathe.wikidot.com/

=Review=
==Sam Putnam==
First comment would be that you're proposing to build a Type 1
replicator, which can be set up with additional jigs and fixtures for
Type 2 replication. :-)

Second comment would be this:

http://cgi.ebay.com/Monarch-CNC-Lathe-YR-1988_W0QQitemZ260502067920QQcmdZViewItemQQptZBI_Lathes?hash=item3ca7221ad0

That's a 19-year-old CNC lathe for a hundred bucks. Granted that it
was probably broken, but a broken lathe is almost always a much
simpler and cheaper platform than a brand-new lathe. If you watch ebay
long enough, you will find another.

Now, you probably need a lathe pretty badly regardless, and a Type 3
lathe is a CNC screw machine with quick-change tool head and workpiece
feed at a bare minimum, so there's no reason you shouldn't get or
develop yourself a Type 1 lathe for Factor E. It would be awesome if
such a design incorporated the idea of eventually adding enough
modular components that the lathe would qualify as a CNC screw
machine.

Moving on to the design you've shown. It's not especially specific but
I see several things that concern me. One is that you seem to be
coupling your hydraulic motor directly to the spindle and headstock.
Normally one isolates the motor with a pulley to prevent vibration
from traveling along the shaft. That's easy enough to fix.

The poured-concrete bed will shrink on you, but you can compensate for
that effect with gibs. Does your design have gibs? I couldn't tell.
Using a single piece of round stock as a ways is going to
enthusiastically bugger your accuracy as soon as you go off center,
and possibly send the toolpost flying. Would you consider a couple
pieces of round stock or T-slot instead? An extruded ways will
probably be simpler/cheaper than cold-rolled steel or scraped bronze
or cast iron, and it matches our emerging design pattern language.

BTW a design based on a cast concrete bed isn't maximally portable.
Some of us live in subduction zones and high Richter events have a way
of cracking monolithic concrete!

For good generality in a CNC lathe, one needs travel along the
carriage and cross-slide, plus rotation of the tool angle, making for
two Cartesian coordinates and one polar. The carriage and cross slide
can be simple lead-screw drives and rotary tables are usually built
with a worm drive. If one wants milling capacity on the same machine,
a Z axis is needed, but for a Type 3 lathe there are two additional
fittings (at least): a robot that feeds workpieces into the chuck and
a quick-change toolhead. That would make it inconvenient to mill on
the same machine one lathes with; it is widely said to be inconvenient
in any case. A mill spins the toolhead while a lathe spins the
workpiece: the two tasks are different enough to benefit greatly from
two dedicated machines.

Concluding comment would be: work with the OpenLathe people, they know
a whole hell of a lot. If you join the googlegroup you'll have access
to a grip of files with a ton of revelant and useful information. Hope
this helps.

== Ben Lipkowitz ==
the rotary table is silly. you ain't gonna need it. the tool post has to be below the centerline, and the rotary table eats up valuable vertical distance.

you should use three points for alignment instead of four. don't make me crawl under the table to loosen the bolts; they should thread into nuts welded under the table and be locked with jamb nuts on the top side. actually, shims would be better: more rigid and compact.

i hope your "base table" is thicker than the two inches in the above diagram. a plain steel bed won't work because it has no damping, and sam doesn't like concrete for some reason (earthquakes, really?) so how about "polymer concrete" - just epoxy mixed with granite aggregate and powder. "it's what the pro's use." anyway, concrete machine tools were very common during WWII and during reconstruction in germany. they can be quite beautiful actually:
http://www.epucret.de/en/products-solutions/product-overview/cast-parts/
http://www.epucret.de/en/products-solutions/product-overview/accuracy/

if i were building a huge lathe to be portable, i'd use a big rectangular tube of structural steel and pack it full of gravel and something viscous like wet bentonite clay or heavy oil.

the original "guide rail" is awful, and two of them would be only slightly less awful. you need full support under the carriage at every point along its travel. that floating bar will flex like mad in the center. for most CNC tasks you tend to do small stuff, so the little XY table might be sufficient on its own, bolted directly to the bed, then unbolted and moved around for doing bigger stuff. speaking of CNC, one huge problem is that there's no spindle through hole, so you can't use a bar feeder.

if you're going to be doing end milling with the angle plate, make sure to size the carriage much wider than it needs to be for lathe work, at least twice as wide as the distance from bed to centerline. also, it has to be mounted to the top side of the XY table.

I suggest making some toy models out of wood or foam or whatever you have lying around.
[[Category:Lathe]]

Torch Table Build

2009-09-09T23:34:10Z

Fenn: /* Review */

=Proposal=

See proposal at http://openfarmtech.org/Lawrence_Proposal.pdf . <BR>
You can also see the working agreement,[[Lawrence Kincheloe Contract]]
<BR>
Previous Work [[Torch Table]] <BR>

[[Image:Overview.jpg|500px|Overview of Blender Model ]]
<BR>
The purpose of this project is to enrich both the participant and the Factor e Farm project. The scope of this specific project is to build the seeds for a MegaRap, which is a modification of the origional Torch Table designed to expand the range of build materials and capabilities. This is in the spirit of the RepRap project, but at a larger scale and lower precision. The initial goal is to design and build a torch table that can be added on to in the future but is still functional in its own right.

=Design Rationale=
*High performance torch table matching and exceedings standards of commercial counterparts
*Ready adaptability to other cutting heads (router, laser, knife, etc.)
*Rack for x, y, and z motion - cheapest, most robust solution for precise motion
*Similar design in x, y, z directions
*Minimal fabrication requriments, bolt-together design
*Spring-loaded x and y motors to maintain traction
*Support under top rail with flat ball bearings to prevent the carrage from jumping the track
*Thin gauge (16 gauge) 1 inch square tubing for light weight strength
*Simple, adjustable carriage design that clamps around the 3 inch cold-rolled rail
*Ways - simplest way according to [http://www.cnczone.com/forums/showthread.php?t=54417 this source] is bearings on cold-rolled steel.

=Bill of Materials=
[[File: BOM Alpha 3.xls|Excel Source Doc]]

[http://www.shender4.com/thread_chart.htm Thread Chart]
{| border="1" {{table}}
| align="center" style="background:#f0f0f0;"|'''Item'''
| align="center" style="background:#f0f0f0;"|'''Discription'''
| align="center" style="background:#f0f0f0;"|'''Amount'''
| align="center" style="background:#f0f0f0;"|'''Cost per item'''
| align="center" style="background:#f0f0f0;"|'''Total per Machine'''
| align="center" style="background:#f0f0f0;"|'''Total Cost'''
| align="center" style="background:#f0f0f0;"|'''Further Info'''
| align="center" style="background:#f0f0f0;"|'''Purpose'''
| align="center" style="background:#f0f0f0;"|'''Aquired?'''
|-
| Computer with parallel port||Total computer system||1||$300 ||$300.00||$300.00 ||http://www.linuxcnc.org/||To run Linux cnc||yes, IBM Laptop
|-
| Xylotex 4 Axis Drive Box || with 4 stepper 425 oz.in. Motors and Cables||1||$460.00 ||$460.00||$460.00 ||Xylotex Stepper and controller||To provide motion control and movement precision||Yes
|-
| PowerPlasma 50 Plasma Torch||Pilot Arc 50 Amps||1||$699.99 ||$699.99||$699.99 ||Everlast||To provide the cutting torch for the cnc torch table||no
|-
| Bearing R6-2RS 3/8"x7/8"x9/3\" Sealed||10 pack||8||$14.95 ||$11.96||$14.95 ||VXB Part Number: Kit711||For preventing the carrage from jumping the track||no
|-
| V-Groove Bearings 3/8 inch||single pack||12||$9.95 ||$119.40||$119.40 ||VXB V-Groove bearings Part number: Kit8407||To provide low friction linear motion||no
|-
| 3/8 inch Hard Fiber Washers||Pack of 100||40||$2.50 ||$1.00||$2.50 ||McMaster Part Number: 95601A330||Holding bearings||no
|-
| Hot rolled steel 3"x1/8" plate||10.0 Ft.||5.32 ft||$12.70 ||$6.76||$12.70 ||Metalsdepot||To provide material for motor mounts||no
|-
| Hot rolled steel 1"x1" square tubes 16 gauge||24ft for $23.28||41.83 ft||$23.28 ||$40.58||$46.56 ||Metalsdepot||To provide structural support||no
|-
| Gear Rack (1/2” sq. x 72” 20 DP 20 Deg)||6 feet per rack||26.83 ft||$24.80 ||$110.91||$124.00 ||Standard Steel Specialty Part Number: 200011||rack for gear to ride on||no
|-
| 3 x 1/8 inch cold rolled Plate||6.0 Ft.||32.33 ft||$17.28 ||$93.12||$103.68 ||Metalsdepot||To provide material to make rails||no
|-
| 3/8 inch threaded rod, Overall Length 36"|| Each||11.43 ft||$1.94 ||$7.39||$7.76 ||McMaster Part Number: 98837A031||for connecting the top and bottom carage||no
|-
| 3/8 inch nuts||Pack of 100||112||$4.20 ||$4.70||$8.40 ||Part Number: 90473A031||For locking threaded rod in place||no
|-
| 3/8 inch washers||Pack of 140||112||$3.23 ||$2.58||$6.46 ||Part Number: 90126A031||For locking nuts and for spacers||no
|-
| Steel 20 Deg Pressure Angle Spur Gear 20 Pitch, 20 Teeth, 1" Pitch Dia, 1/2" Bore||Each||4||$15.37 ||$61.48||$61.48 ||McMaster Part Number: 5172T12||Attaches to stepper motors and interfaces with gear rack||no
|-
| sleeve bearing||Each||4||$1.34 ||$5.36||$5.36 ||McMaster Part Number: 6391K143||to connect between the stepper motor and the gear, will also add a bit of adjustable length||no
|-
| 10-32 set screw 7/16"||per Pack of 100||4||$5.44 ||$0.22||$5.44 ||Part Number: 92311A428||Set screw for attaching spur gear, sleeve bearing to stepper shaft||no
|-
| Zinc-Pltd Stl Pan Head Phillips Machine Screw 10-32 Thread, 1-3/4" Length|| Pack of 100||8||$8.45 ||$0.68||$8.45 ||McMaster Part Number: 90272A837||Connects the mount plate arms to the carrage||no
|-
| Zinc-Pltd Stl Pan Head Phillips Machine Screw 10-32 Thread, 2-1/2" Length||Pack of 100||48||$6.58 ||$3.16||$6.58 ||McMaster Part Number: 90272A840||For connecting the rail, rack, spacer and c channel||no
|-
| Zinc-Pltd Stl Pan Head Phillips Machine Screw 10-32 Thread, 3/4" Length||Pack of 100||24||$5.11 ||$1.23||$5.11 ||McMaster Part Number: 90272A831||For mounting the stepper motor to the mount plate||no
|-
| Zinc-Plated Steel Machine Screw Hex Nut 10-32 Thread Size, 3/8" Width, 1/8" Height||Packs of 100||80||$1.55 ||$1.24||$1.55 ||McMaster Part Number: 90480A195||For locking the mount plate swing tightness, tightening the rack and locking the stepper motor in place||no
|-
| Nylon 6/6 General Purpose Flat Washer Off-White, No. 10 Screw Sz, .44" OD,.02"-.04" Thk||per Pack of 100||32||$3.83 ||$1.23||$3.83 ||Part Number: 90295A120||allows the motor to swing freely||no
|-
| stepper spring||pack of 6||4||$10.00 ||$6.67||$10.00 ||McMaster Part Number: 3114T79||Prevents stepper motor shaft from crunching ||no
|-
| Multipurpose White Lithium Grease 10.25-Ounce Net Weight Aerosol||single pack||1||$5.62 ||$5.62||$5.62 ||McMaster Part Number: 1380K29||For greasing rails, bearings, gears, rack, etc…||no
|-
| Bright Finish High-Speed Stl Spiral Point Tap 10-32, H2 Pitch Diameter, 2 Flute||single pack||1||$5.26 ||$5.26||$5.26 ||Part Number: 2523A469||For tapping the 10 gauge threaded hole in the brass bushing and the steel bearing||no
|-
| 10 gauge drill bit||single pack||1||$1.74 ||$1.74||$1.74 ||McMaster Part Number: 2930A21||For drilling holes in rail, stepper plate, stepper plate swing||no
|-
| Gen Purp Black Oxide HSS Jobbers' Drill Bit 3/8", 5" L Overall, 3.1" Drill Depth, 118 Deg Point||single pack||1||$4.46 ||$4.46||$4.46 ||Part Number: 2931A34||For drilling holes in rail for threaded rod||no
|-
| Gen Purpose Uncoated HSS Jobbers' Drill Bit Wire GA 18, 3-1/4" Oal, 1.9" Drill Depth, 118Deg Point||single pack ||1||$1.52 ||$1.52||$1.52 ||Part Number: 30585A29||making the hole for the 10 gauge tap. It has to be slightly smaller than 10 gauge because we need to cut threading into it.||no
|-
| Military Spec Cadmium-Pltd Steel Flat Washer No. 10 Screw Sz, .44" OD, .03"-.07" Thk, MS27183-8||Pack of 100||1||$1.94 ||$1.94||$1.94 ||McMasters Part Number: 98032A469||Small enough to fit on the rack, big enough to do some good. General purpose metal washers for 10 gauge screws.||no
|-
| Total per machine||$1,960.19||||||||||||||
|-
| Total Cost||$2,034.74 ||||||||||||||
|}

=Working Concepts=
==X axis==
[[Torch_Table_Xaxis | X axis BoM details]]
[[Image:xaxisconcept.jpg|500px]]
[[Image:X axis back view.jpg|500px]]
[[Image:X axis front view .jpg|500px]]
[[Image:X axis top plate stepper mount and y axis mount.jpg|500px]]
[[Image:X axis bearing shot wire frame.jpg|500px]]
[[Image:X axis bearing shot.jpg|500px]]
[[Image:X axis barrel .jpg|500px]]

==Y axis==
[[Torch_Table_Yaxis | Y axis details]]
[[Image:yaxisconcept.jpg|500px]]

[[Image:Y axis back view.jpg|500px]]

==Z axis==
[[Torch_Table_Zaxis | Z axis details]]

[[Image:Y axis z axis front view.jpg|500px]]

[[Image:Z axis shot.jpg|500px]]

=Blender Concept=

[[Image:torchconceptlawrence.jpg|500px]]

=Blender Design File Download=

[[File:Factor e Torch Alpha 3.1.blend]]

=Plasma Torch=

==Torch vs. Plasma Cutter==
*Comes down to initial cost versus long-term cost
*Plasma cutters - consumables cost $20 for 5 new electrodes and nozzle heads
**Electrodes are rated for 45 minutes to 60 minutes for 1/2" steel
**More expensive versions state they last 4 times longer - are heavier and have better temperature control
**For anything above 1 inch, torch is better
**Can be interfaced with a computer cheaper than Torch

==Desired Characteristics==
We are looking for a machine rated for 1" milled steel that will cost roughly between $700-$1100. We are limited on budget because we are funded primarily through donations at the moment.

Since we want to use the machine for cnc work, we are interested in the pilot arc starting, or touch off starting. We could also use high frequency starting, but we would have to shield our motor controller and any other equipment in the area. Would it be possible to shield the plasma cutter? We want to be able to cut thin material with the torch so it is likely we will want the pilot arc starting feature.

Do you have any suggestions on a best practice method of attaching a plasma torch head on a cnc machine?

We would also be interested in a plasma cutting head that would be easier to mount. Currently in your accessories page you only list a model that is appropriate for plasma cutting by hand. Also, since this machine needs to be flexible we would also like the option of using the plasma cutting head by hand. Through looking at competitors websites, its clear that its easy to offer one or the other and switch them at the DC power inverter, but how easy would it be to add a 45 degree flexible head that can be fixed for either cnc overhang cutting or hand cutting? This seems like an easy adaption, but I might be missing something.

Also, we are interested in the engraving feature. Especially the controlled plasma pulse feature. The reason is that we are interested in precision surface removal, and gouging because we have an idea to use this machine as a plasma lathe, combined with a cnc controlled head. This isn't a requirement, but we are very interested in getting the maximum amount of utility from this tool.

==Plasma Cutters Considered==
[http://www.everlastgenerators.com/PowerPlasma%2060-317-pd.html Everlast]
*cheap ($800)
*5 year warranty
*made in china
[http://www.affordableplasmacutters.com/page/58118206 60 Amp Parker MP]
*cheap
*1 year warranty
*made in america
*Out of stock/high frequency start only
*Appears to have equivalent performance to Esab Powercut 1250
[http://www.weldingmart.com/Qstore/p002778.htm Esab Powercut 1250]
*Expensive ($2700)
*Brand name

==Plasma Cutter PC Interface==
[[Image: Relay circuit.jpg |200px|sub]] [[Image: Newfoorpedalwiring.jpg|200px|sub]]

(ciruit drawn with [[http://www.weldingmart.com/Qstore/p002778.htm open source circuit simulator]])

A simple relay circuit, the components depend on the plasma cutter interface.
Since the Xylotex stepper controller pipes out unused pins to a second parallel port, we'll isolate the parallel port using an optoislolater and switch on a relay switch which replaces the manual torch ignition switch. If the torch allows for proportional current control, usually done with a voltage divider circuit built with a potentiometer, then we might use a pwm modulated rheostat control with the computer providing the pwm signal. If all that fails, there is alway hacking into the plasma cutter circuit board and taking over control using a microprocessor... maybe version 2.

==Linux CNC==
[[http://linuxcnc.org/ LinuxCNC]]
===The Setup===
We are as of Sept. 4, 2009 using an IBM ThinkPad laptop graciously donated to the cause by Inga. It has the latest EMC2 installed
from the Ubuntu 8.04&EMC2 Live CD.

If your starting from a pre-existing Linux install, like I was, then read [http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl this important user contributed wiki.] I had to reinstall using the 8.4 live cd because 8.10 of Ubuntu wasn't supported.

Once you get that all installed, the best documentation available is from the user contributed wiki and the included manuals. For example, when I had trouble with getting the IBM laptop to talk to the motor controller, I used [[http://www.distinctperspectives.com/emc2installsetup/ this walk-through]] to step me through a working install which lead me to the actual problem of the IBM laptop having a non-standard printer port address.

Once I got the stepper motors twitching to my every whim, I put it all down and will continue from where I left off once I get the little beasties mounted.

==Torch Table Trouble Shooting==
For those extra hard to reach bugs
*Check stepper motors
**They should turn when powered off, so the whole table should move freely. If it doesn't fix it.
**When the motor controller is powered on, with the PC disconnected, the stepper motors should be locked in place or provide significant resistance.
**If everything checks out, the motor driving circuitry and the stepper motors are at least working correctly.
*Check the PC parallel port.
**You can do this with a multimeter and LinuxCNC. If you test one of the pins under control and its jumping around like crazy then the computer is at the least sending something with the parallel port
**There are options to change the parallel port address from the default. In the case of the IBM laptop, the parallel port was 3BCH, which is a hex value.
*Check the pinout of the cable.
**In our case we used a shielded straight pass through cable, which means each pin on either side corresponds to its matched up pin on the male/female connector.
**If its different than what you think it should be, according to whatever motor controller your using. You can adjust the pin out in EMC2. Look up how to do this.
*Check installed version of Linux.
**In the version we used, there was an issue where the kernel drivers for 8.4 weren't compatible with 8.10 and above. This means that it installed fine but there wasn't an option for using the special real time EMC2 kernel. The fix is to reinstall using either the live CD which will leave you with a clean Ubuntu install with the software already installed (very convenient if it works), or installing from scratch Ubuntu 8.4 and installing the package seperately from [[http://linuxcnc.org/]]

=Build Steps=
This table uses standard stock steel parts with no finishing besides the finishing that is required.

If you caught that, then you have two options. Find a local machine shop to cut out all that steel you just purchased or live with some inaccuracies which should be adjustable.

==Necessary Tools==
*Something to cut accurate holes with
*Something to cut 3/8 inch treaded rod, 1/8 inch hot rolled steel plate, 1 inch tubing, etc...

==Tools We Used==

===Building a Jig===
Yes its a technical [http://en.wikipedia.org/wiki/Jig_(tool) term.]

For our purposes we need a reliable way to drill somewhat precise holes quickly.

To do this we need to constrain the rack in the x y and z direction during drilling but allow movement along the y axis to reposition the rack for the next hole. In this example, the direction along the length will be our y axis.

There are several products out there that will do what we want, but they all need to be modified slightly for our purposes.

For drilling the holes, you'll need a guide made out of something that won't mar the metal. Wood or plastic works nicely.
If you have a vice or an x/y milling vice, these will work nicely although you'll have to make some sort of insert so the gear rack can slide easily in the vice channel. Here again wood or plastic are your friends.

If you don't have a vice and you do have some wood and some nuts and bolts that fit the mounting holes in your vice, you can make a temporary jig with blocks of wood which have to be aligned such that the drill head is above the rack, doesn't crater into the mounting plate (unless your wise enough to put a spacer block under the rail) and constrains the rail in the x direction while allowing free movement in the y direction. It'll take some practice but once you get it, you can use the same setup for all the rack.

The process is fairly simple, you mark your first hole on the rack and then every succeeding hole, you measure 8 inches (what we used) from the center of that hole. This can be achieved by adding a guide which you line up the center of the hole you just drilled with the guide such that the drill bit is over the next spot and the last drill hole you made is 8 inches away.

Lastly, you clamp down the rack in the z direction such that frictional forces and the wood blocks help constrain the rack for drilling. Releasing the clamp slightly until the rack is movable along the y direction again allows you to position the rack for the next hole to be drilled.

==The Table==
[[File:Work in progress of torch table frame.JPG| 400px|sub]]
[[File:Work In Progress Torch Table Leg.JPG| 400px|sub]]
[[File:Work In Progress Joint.JPG| 400px|sub]]

=Review=

Please submit comments here. Please review our design rationale first.

Particular points:
*Suitability of 3x1/8" cold rolled rail as a guide
*Suitability of thin gauge 1" square tubing for most of the gantry
*Structural or stability issues?
*Acceleration issues?
*Feasibility of using a laptop and compromises therefrom?
**run [[http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Latency-Test realtime latency test]] before getting too attached - laptops are notorious for hardware timing glitches.
**dust generated by plasma will get in keyboard and fan, wear out quickly. hard to replace laptop parts.
*Suitability of plasma cutter?
*Potential improvements?

=Team=
*Deep in the continental US underground...
[[Image:workteam.jpg]]

[[Category:Torch Table]]

Ben Lipkowitz

2008-10-16T23:03:39Z

Fenn: obfuscate my email addy

ben lipkowitz <fenn [@] sdf.lonestar.org>
to Marcin Jakubowski <joseph.dolittle@gmail.com>,
date Thu, Mar 6, 2008 at 5:46 PM
subject Re: thin client EMC

hide details 5:46 PM (20 hours ago)

Reply

On Thu, 6 Mar 2008, Marcin Jakubowski wrote:

> Hello Ben,
>
> Thanks for the excellent recommendation. Please send me a Netier or two. Let
> me know if you need some cash. We're cash poor, we do everything on
> donations, and we are working hard on a fundraising mechanism for the open
> source product development consortium that we are proposing. It's starting
> to move forward.

It keeps your technology appropriate, at least. I'm cash poor too, but
stuff's just going to sit in the basement anyway.

> I read your blurb on USB compact flash. Can I just boot off that? I have a 1
> Gig card.

USB isn't compact flash...? You would need an adapter from CF card to
ribbon cable connector, but I can supply the cable if I can find it. I
haven't tested booting off USB yet, and there is a chance even if booting
works that it will interfere with realtime stuff.

> I'd like to ask you, in case it's tricky to get all the right parts working,
> to send me a package with all the necessary components, and I'll gladly pay
> you for the pieces.

I dont have "all the pieces". I wish I could send a turn-key three axis
servo system, but I'm just not there yet. An iso image to run on a thin
client hasn't been put together yet either. A really lightweight
emc2-compatible-out-of-the-box linux distro would certainly be welcomed by
the emc community, but for now we'll have to slog through setting up a
stock Debian net-boot image and then adding the emc2 packages to it.

> We will be utilizing the torch table to do a second prototype of the CEB
> machine. We will be using the CEB machine to build our open source product
> devevlopment facilities. We aim to start building in the beginning of May.
> We have all this development work to be done by that time, so we need to
> move fast.

I hope I'm not just getting in the way then; you might be better off with
a desktop and steppers, and fix it later if you dont like it.

Your vision is really cool; high-tech self sufficiency is something I've
been thinking about for years but never manage to get anything done. It
started with tesla turbines and then a scratch-built metal lathe:
http://fennetic.net/machines/lathe_modifications

> If you can jumpstart me in the right direction with the thin client, I'd
> appreciate it greatly. Please let me know what I should read, and if you can
> point me to a procedure, that would be great. Tell me more about the servos.

read this for starters: (not exciting, how to set up PXE net-boot)
http://www.debian-administration.org/articles/478

I think our emails passed like trains in the night. In any case, the servo
drive is a simple h-bridge and encoder counter, which talks to a chip
which talks to the parport. If I only had two or three axes then this
would be "easy" to interface directly to the parallel port, but with six
or seven axes things look a little different.

here is my wiki page with some chicken scratch:
http://fennetic.net/machines/motherchip

> What do you do for a living? We're doing this open source product thing full
> time.

I'm supposed to be developing this into an online business, sold as a kit:
http://fennetic.net/machines/index.php?hextatic
but keeping focused is difficult when working alone. I end up spending a
lot of time in #emc on irc.freenode.net. It will be "open source" but I'm
not sure that public domain is the best way to do it.

I just read "the four hour workweek" - perhaps it could help you to refine
your business plans. Yes it reads like an infomercial, but there is a lot
of good advice regarding "time management" = making money without spending
all day doing it, how to not babysit people, and how to take advantage of
modern tools like google adwords. Understanding how things are done in
"the real world" (where your target audience is non-geeks) can help to
clarify what is good and what is bad about it. Maybe it's no big deal if
you already know this stuff, but they sure don't teach it in school.

I've done some linux system administration (perl and mysql hell) but it
doesn't really pay the bills. I'm thinking about joining Neil
Gershenfeld's fab-lab group but so far I've been too chicken to ask.

ciao,
-fenn
812-331-0654
[[Category:Collaboration Discussions]]